Safety device for presses



Jan. 4, 1944.

H. W. SUNDSTROM SAFETY DEVICE FOR PRESSES Filed Feb.

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strom attorney 3nnentor 3 Patented Jan. 4, 1944 UNITED STATES PATENT OFFICE SAFETY DEVICE FOR PRESSES Harold W. Sundstrom, Worcester, Mass.

Application February 27, 1943, Serial No. 477,467

3 Claims.

This invention relates to safety devices for presses and the like, and more particularly to a safety guard which is movable to and from a position where it prevents injury to the machine operator during a work forming operation.

It is the primary object of myinvention to provide an automatically operated guard for a press and similar types of machine tools which will effectively prevent injury to the operator during the step of forming the work piece, and particularly which will interpose a barrier capable of preventing or hindering insertion of the operators hand into the work zone during the danger period and of stopping fragments of metal flying from a broken punch or the work.

A further object of the invention is to provide a guard mechanism which is so constructed and arranged that when the punch descends the guard will move quickly to a guarding position and dwell there while the work is being formed, or while an automatic knockout mechanism serves to remove the work when the punch ascends, and yet which provides ample time and opportunity for placing a new piece of work in position. in the following disclosure.

Referring to the accompanying drawing illustrating the preferred embodiment of this invention as applied to a punch press:

Fig. 1 is a vertical front elevation of a punch press having the ram in its uppermost'position and the guard out of the way;

Fig. 2 is a similar view with the punch in its lowermost position and the guard in front of the work; and

Fig. 3 is a fragmentary side elevation of the swinging guard and the cam operating mechanism.

In accordance with my invention, I have provided a swinging guard for a power or a manually operated press or similar type of machine tool wherein the construction is such that a guard moves quickly to a guarding position in front of the work zone when the tool descends and remains there during the entire period of potential danger. This movement is accomplished by means of a cam so shaped and arranged as to provide a dwell in the movement of the guard prior to the work forming operation and preferably at each end of the operating stroke of the tool.

The invention is illustrated in the drawing as applied to a punch press which may be of any suitable construction. It may comprise a ram 1 arran d to be rec prooa ed vertically 126,-

Further objects will be apparent tween suitable slideways II by means of a crank pin I2 on a crank l3 which is revolved by means of power mechanism, such as a shaft and pulley i4 suitably supported on. the machine frame. The ram is pivotally connected to the crank pin by means of a pitman or connecting rod l5 and a pivotal coupling [6 of suitable or standard construction. The connection may comprise an adjusting screw on the pitman and a nut I1 secured to the coupling which are so arranged as to vary the height of the ram or the tool space and permit the use of different types of tools and different thicknesses and types of work and die.

The preferred form of guard mechanism comprises a guard plate suitably secured on the lower end of a rod 26 which is pivotally mounted on the press and arranged to swing the guard laterally across the front of the press and between the work zone and the normal position of the operator. The rod is preferably adjustably affixed to a pendulum or swinging plate 21 that is pivoted on a pin or screw 28 removably secured to the upper stationary part of the press frame,-such as on the U-shaped standard 29 affixed to the main frame of the press by suit.- able screws. The guard plate is made of wood or metal of such size and shape that it will hinder or prevent access to the operating zone from the normal position of the operator when standing in front of the machine. The rod 26, which may be made of wood or metal, is strong enough to Withstand the blow of forcibly removing the operators hand if he carelessly leaves it there while the punch descends.

One feature of this invention lies in operating the guard by means of a cam and follower, one of which is mounted on the pendulum and the other on a movable part of the press, and wherein the shape and location of the cam member is such as to cause a dwell at the lower end of the tool stroke. It is preferred that the cam be secured to the pendulum and that the follower be located on the revolving crank. As illustrated, the plate 2'! is provided with a cam slotv 30 within which slidably rides an enlogated cylindrical cam follower or roller sleeve 32 that is pivotally mounted on an oscillatable pin 23 serving as a bearing. This. pin passes through two, upstanding lugs 34 on the top of the crank pin bearing 35 and it is suitably secured in position, as by means of the nuts 36. The cam roller 32 is of such a size as to fit snugly within the substantially parallel walls of the slot 30 of the cam plate nd it. reciprocates horizontally and vertically as the crank pin l2 revolves, the roller 32 being made long enough to permit it to slide both vertically and horizontally within the cam slot without its leaving contact with the cam plate.

The cam plate is preferably substantially S- shaped so as to provide a dwell at each end of the tool stroke. The slot 30 is therefore so shaped that its upper end is vertical and in alignment with the center of the pivot screw 23 when the guard is in its outermost and inoperative position, as shown in Fig. 1. The slot is also so shaped that when the guard has been swung to its operative guarding position, as shown in Fig. 2, then the lower part of the slot is vertical and substantially in alignment with the supporting screw 28. The intermediate portion of the cam slot makes an angle with each of these two end portions as clearly shown in the drawings and it is arranged at such an oblique angle that the guard swings rapidly to a guarding position.

The rod 23 is preferably secured to the cam plate 27 by adjustable eye bolts 38 and 39, one of which, such as the upper one, has an elongated slot therein, while the other substantially fits the round rod 26. Thus, by loosening the bolts, the rod may be swung laterally relative to the cam plate 21' and so position the guard 25 as desired to cover the operating zone of any of the various types of machines to which the mechanism is applied.

The parts of the pendulum are so made that the cam plate may be reversed and thus made to swing from left to right or from right to left depending upon whether the operator of the machine is left or right handed. In the construction shown, the guard swings to the left and thus moves the hand of a right handed operator towards the left when the working zone is to be guarded. The cam slot 33 is also preferably made long enough so as to be applicable to presses having different throws of crank pin.

The rod 26 may be moved vertically through the clamping screws 28 and 29 so as to position the guard 25 properly for different sizes of die and for different positions of the operating zone, as is sometimes required when the height of the ram or the tool space is adjusted by means of the adjusting screw on the ram.

The operation of the device is such that the guard 25 is in the position of Fig. 1 when the work is to be placed in the operating zone. When the press is started and the punchdescends, the cam roller 32 first rides down the vertical portion of the slot 3i] without affecting the position of the guard 25, thus giving the operator a little more time for locating his work and removing his hands from the operating zone. When the roller 32 passes from the vertical to the oblique portion of the cam slot 39, the guard 25 is moved rapidly towards the left to the ultimate position of Fig. 2, at which time the cam roller 32 enters the lower portion of the slot which is now vertical. Then the cam roller may move further downwardly without affecting the position of the guard 25. As the driving crank pin starts upwardly again, the cam plate remains stationary while the pin 32 rides up the vertical part of the slot, and thus the guard 25 remains in place to permit a knock out mechanism, if one is used, to remove the work from the operating zone. That is, the guard remains in place for an appreciable time before and after the punch engagesthe work. The guard 25 swings rapidly to the inoperative position of Fig. 1 while the cam roller goes up the slanting portion on the cam slot, and when the roller enters the vertical portion the guard 25 remains stationary as the crank pin l2 completes the upward movement and begins a new stroke.

If the cam slot were substantially straight without the dwell portion at each end, then the required movement of the swinging arm would be too slow on the down stroke of the tool and the working zone would not be covered soon enough and a mans arm might not be swept out of the path quickly enough to prevent injury. It is, therefore, important that the immediate portion of the slot be arranged at a steeply oblique angle relative to the ends of the slot so as to cause a quick swinging motion of the guard. The lateral distance of travel of the cam roller across the face of the cam plate is intended to be only enough to provide sufiicient clearance for the operator to work easily and comfortably at the machine. The dwell periods provided by the two ends of the slot are therefore useful in that they protect the operator and give him ample time for his work, while the intermediate quick motion portion of the slot gets the guard to and from its operative position without any loss of time. By locating the pivot 28 at the top of the press and mounting the cam follower on the crank bearing, I have provided a short lever arm for the cam follower and a long lever arm for the guard, so that the guard is moved sufficiently far from the work zone by means of a comparatively small cam plate.

It will now be appreciated, in view of the above description of this invention, that various modifications may be made in the structure and arrangement of the parts as may be required by different types of machines to which it may be applied. However, the construction is almost universal in that it may be applied to all sorts and types of machines without rebuilding or requiring any more than the simple adjustments permitted by the construction above described.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent is:

1. In a power press having a frame, a reciprocable ram, a tool thereon and a crank above the ram connected to reciprocate the ram and tool, a guard, a swinging arm carrying the guard which is pivotally mounted on the frame above the crank and arranged to move the guard laterally in a plane substantially parallel with the crank axis and to and from a position in front of the work, a cam mechanism including a cam plate and a cam follower, one of the parts of the cam mechanism being connected to the arm and the other fixed on the crank so as to move the swinging arm as the crank revolves, said plate having a cam surface shaped to swing the arm to a guarding position when the tool descends.

2. In a power press having a frame, a reciprocable ram, a tool thereon and a crank connected to reciprocate the ram and cause the tool to operate on a piece of work, a guard, a cam plate pivotally mounted on the frame above the crank and connected to swing the guard laterally to and from a guarding position in front of the work zone, an elongated, vertically oscillatable cam follower fixed on the crank and contacting said cam as the crank revolves, said cam having an S-shaped slot shaped to provide an intermediate obliquely arranged surface which causes the follower to swing the guard laterally, each end of the slot being in a substantially vertical position when engaged by the cam follower so as to provide dwell periods for the guard when the direction of travel of the tool is reversed.

3. In a power press having a frame, a vertically reciprocable ram, a tool thereon for operating on a piece of work and a revolvable crank connected to reciprocate the tool, a guard, a pivot on the frame above the crank, a cam plate reversibly mounted on the pivot to swing laterally in front of the crank, means for mounting the guard on the cam plate and adjusting its vertical position and the lateral throw thereof, an elongated cam follower mounted on the crank and engaging the cam as the crank revolves, said cam being a substantially S-shaped slot having an oblique portion which causes the guard to move rapidly to a guarding position while the ram descends and having a lower end portion which is substantially vertical when engaged by the follower so that the guard dwells in front of the work zone before, during and after the tool operation on the work.

HAROLD W. SUNDS'IROM. 

